I think 4x Boomkin are going to be insane. Now their Root abilities are AE--They affect everyone within 8 yards. That plus SOLAR BEAM is going to be insane. Absolutely insane.
I stopped leveling my Druids and went back to my Shaman after seeing some of the beta videos and reading some beta personal accounts. I think Shaman are going to be, without question, the best boxing setup in Cata.

The only "random" thing added to their DPS is that Lava Burst can randomly reset. Compared to many of the other classes' catches that were added to randomize their DPS rotations a bit this is cake to deal with.
Mosg2-- You sound like me. I have hourly debates on whether I am going to play my 5xBoomkins or 4xShamans...
Or maybe 1xBoomkin+4xShamans. Root them and then nuke them!

Which comp do you think you'll play at release?